VASCULAR DISORDERS OF THE KIDNEY
Renal artery stenosis of any etiology causes decreased blood flow to the involved kidney, with resulting secondary hypertension that is often not responsive to anti-hypertensive medications. Treatment is usually surgical.
• Atheromatous plaque is the most common cause of renal artery stenosis.
• Dysplastic lesions (“fibromuscular dysplasia”) are an important additional cause of renal artery stenosis.
• All 3 lesion types occur in middle-aged adults.
o Medial fibroplasia with aneurysms (most common) causes alternating stenosis and aneurysms in “string of beads” pattern on arteriography
o Perimedial fibroplasia involves the outer media
o Medial hyperplasia
• Miscellaneous diseases that can affect the renal arteries (with or without ste nosis) include congenital anomalies, Takayasu arteritis, and radiation injuries.
Benign nephrosclerosis is caused by hypertension. The kidneys have a finely gran-ular external surface and on microscopy show hyaline arteriolosclerosis, tubular atrophy, interstitial fibrosis, and glomerulosclerosis. Lab findings include mild pro-teinuria, hematuria, and azotemia.
Malignant (accelerated) hypertension can damage the kidney, causing fibrinoid necrosis of arterioles, glomerulitis, and hyperplastic arteriolosclerosis. Clinically, it causes cerebral edema, papilledema, retinal hemorrhage, intracerebral hemorrhage, and oliguric acute renal failure. The cortical surface shows pinpoint petechial hem-orrhages (“flea-bitten” look).
Renal infarction is due to thrombi from the left side of the heart, atheroembolic disease, and vasculitis. It presents with sudden onset of flank pain and hematuria. Small infarcts may be asymptomatic.
Sickle cell anemia can cause medullary infarctions due to blockage of blood flow in the medullary vessels, which can result in asymptomatic hematuria, loss of urine concentrating ability, renal papillary necrosis, and pyelonephritis.
Diffuse cortical necrosis can cause anuria; the condition can occur with obstetric emergencies and disseminated intravascular coagulation.